A storage medium such as a memory card or a flash media card is a data storage device and can be used in electronic devices and systems, including digital cameras, mobile phones, laptop computers, media players, video game consoles, etc. The storage medium can be re-recordable, and can retain data without power. A card reader is attached to a host, e.g., a personal computer, and has a socket to connect a storage medium. When a storage medium is coupled to the socket, the card reader can transfer data between the host and the storage medium.
FIG. 1 shows a conventional data transfer system 100. The data transfer system 100 includes a host 102, a controller 104, and a storage medium 108, e.g., a flash media card. The controller 104 includes a data transfer unit 110, a control unit 112, a filter 124 and a socket 106. A data path, including the data transfer unit 110 and the data lines 165 and 152, is used to transfer data between the host 102 and the storage medium 108. A control path, including the control unit 112, the filter 124, and the control lines 164, is used to control the data transfer of the data transfer system 100.
The control unit 112 and the filter 124 monitor the status of the storage medium 108, e.g., whether the storage medium 108 is coupled to the socket 106. In operation, if the storage medium 108 is coupled to the socket 106, the socket 106 generates a monitoring signal 150 to the filter 124. The filter 124 removes noises of the monitoring signal 150 and provides the status signal 154 to the control unit 112. The control unit 112 further includes a card detection circuit 122 and an interruption circuit 120. The card detection circuit 122 coupled to the filter 124 receives the status signal 154 and enables the data transfer unit 110 if the status signal 154 indicates that the storage medium 108 is coupled to the socket 106. The interruption circuit 120 generates an interruption signal 164 in response to the status signal 154. The interruption signal 164 is transferred to the host 102 according to a standard interface protocol, for example, Peripheral Component Interconnect-Express (PCIe), Universal Serial BUS (USB), Serial Advanced Technology Attachment II (SATA2), or Advanced Technology Attachment (ATA). Upon receiving the interruption signal 164, the host 102 reads the status register of the interruption circuit 120 to obtain the status information of the storage medium 108. If the storage medium 108 is coupled to the socket 106, the host 102 can control the data transfer unit 110 to exchange data with the storage medium 108.
However, when the storage medium 108 is decoupled from the socket 106, the control unit 112 keeps being powered on, such that the control unit 112 can generate the interruption signal 164 once the storage medium 108 is inserted again. As such, the power consumption of the data transfer system 100 is relatively high.